I just finished my tbi to carb swap and im using the stock tbi pump in tank and using a return style holley fuel pressure regulator. my problem is not matter how much i screw or unscrew the adjustment on the regulator it stays the same. wont drop or raise pressure at all. i have a guage mounted on a brasss Tee that is screwed in to the regulator and feed fuel line. i have the return hooked up right. obvisouly its gotta be a problem with the regulator right guys? also when i leave my alternator unplugged the fuel pressure sits around 7psi i noticed this cuz i accidently had it unplugged and plugged it back in and thats when the pressure went up to 12 psi or so. im using a edelbrock carb 750 which is sorta big for my 350 but i plan on gettin it tuned right soon.

 

heres the problem, the tbi in the tank is way too much pressure for a carb. I had same thing. theres only 1 pressure regulator that summitt racing sells I think its a mallory that will regulate from like 35-40 pounds down to 5. its around 100$ or more. what you can do is get a holley blue or red electric pump, or use a mech pump on the side of the block w/ your regulator.it sounds like you drive it on the street, any street carb should'nt have no more than 5-6 psi. check your floats while @ idle. I left stock pump in tank and pulled the fuse to the pump. and ran a mech pump.since than I bought a holley red pump/ reg but have'nt installed it yet.

 

thanks for the info, i thought the TBI pump only put out like 15psi so i figured that this regulator would regulate that down to a desirable carb psi. i think im just gonna return this regulator to summit since it also started leakin around the top plate of it where you adjust the pressure. i think il just do what you said and get a mechanical pump.

 

tbi pump is about 20psi. unless its been replaced. most replacement pumps are 40ish psi. regardless, any return style regulator should be able to handle it. most common problem with regulators not adjusting pressure right is a cloged return line.

 

So glad I found this post. And sorry I have to bring it back. I'm having the same problem. Except my 3 port holley regulator is only letting 2psi come through. I'll explaing what I've done to the car.


It's a 91 Camaro rs 3.1 v6. That motor blew up so I swapped in a carb 350 and I'm still using the stock fuel pump. Car idles fine but driving down the road it's starts sputtered and acting like it's getting no gas. When i close of the return line the psi pops up to 4psi and as soon as I let the line loose it drops back down to 2.

I was think of try to install a valve and set it up it where it sets my pressure back to 4.

What are your two cents? Think it will work?

 

seems like something is wrong with the regulator, you should be able to adjust it much higher

 

Mallory 4309 Adjustable regulator. I run an in-tank 255lph Wahlboro pump on my carbed 84 and have zero issues with it.

@ Curtalert89 Check your lines to and from the regulator. Sometimes the ribs on the ports that the lines go over cut into the inside of the lines, creating blockage.

Pull your ports off to the tank and blow air through them. Do you hear bubbles in the tank? Reseat your lines and make sure they're clear before putting them back on.

 

@ Ozz1967 Are still using the mechanical fuel pump off the block as well?

 

No. Mine is blocked off. I am using an aftermarket 255 Wahlboro tpi-style in-tank electric pump.

 

Thanks. Here's my scoop. Stroker motor going in my 86. Got a Walbro 255 in yesterday and ordering a bypass pressure regulator soon. Was trying to figure out what to do with the return lines off of the mechanical fuel pump and the regulator. With the Wabro and bypass
regulator, do I need the mechanical pump or get one with out a return?

 

You totally bypass the mechanical block pump. I would get a block off plate and remove the mechanical pump completely.

Run feed line from tank into the bypass regulator. Feed line from regulator to carb. Return line from bottom of regulator to return line to tank.

You MUST have the return hooked up to keep the in-tank pump cool.

7psi max is your pressure setting.

 

Thank you sir.